1. Field of the Invention
The present invention relates to printers. More particularly, the present invention relates to ink jet printers.
2. General Background of the Invention
The advent of CMOS print heads allowed the integration of print head drivers into the print head silicon. Firing nozzles require a large current in the print head resistor for a very short duration.
Typical ink jet printers have an energy distribution system similar to FIG. 1. Typically, there are five energy storage “capacitors” containing energy supplied to the printer. Print head firing, actual heating of the print head resistor, is very fast, thus the capacitors further from the print head provide little energy during the firing. The fifth capacitor located close to the print head supplies the current used to heat the print head resistor, which forms the ink drop to be ejected to the paper. The capacitor 5 on the carrier card is close to the print head but its location is still removed from the print head silicon. The current required by a print head is very large, often as much as 5-10 A instantaneously. Any capacitor Equivalent Series Resistance, ESR, or inductance, developed from trace width/spacing, causes voltage ringing at the print head silicon. This impedance restricts current available for print head firing and affects print head firing performance and as well can damage the print head electronics by creating overvoltage spikes. In addition, as the number of firing nozzles increases, the current increases. This current variation generates larger voltage and energy variations at the print head silicon. The goal of good energy distribution is to provide a constant voltage and current to each nozzle as the nozzle is fired. This goal is limited by the capacitor ESR and circuit board Lan length.
The following patent documents, and all patents and patent documents mentioned herein, are incorporated herein by reference: U.S. Pat. Nos. 6,278,470; 6,199,969; 6,158,857; 6,099,101; 6,019,461; Japanese patent document nos.: JP 11138803; JP 5130054; JP 62193853; and JP 60009775.
U.S. Pat. No. 6,199,969 to Halfinger et al. describes a method and system for detecting nonfunctional elements in an ink jet printer. A switching power supply is coupled to the print head to supply power to the print head. An output capacitor is coupled to the output of the switching power supply to store a DC voltage. An output shifting circuit is coupled to the switching power supply to shift the voltage level across the output capacitor between a low state and a high state. A test current discharging from the capacitor when an element of the print head is activated is then measured. The measured current is then compared with a reference current to determine if an element is nonfunctional.
The '969 patent discloses a capacitor coupled to the print head cartridge of an ink jet printer that switches between a high state and a low state.
U.S. Pat. No. 6,019,461 to Yoshimura describes an ink cartridge that has a memory device on which information about the ink cartridge is stored. A controller in the printer determines whether the attached cartridge is suitable for use with the printer by comparing the information in the memory with reference data stored in the printer. Alternatively, a capacitor having a capacitance value corresponding to the type of ink cartridge may be placed on the cartridge. The printer then determines the type of ink cartridge based upon the sensed capacitance of the capacitor on the print head cartridge.
Japanese Patent No. 11138803 to Kazuhiko discloses an ink jet type recording apparatus that uses a capacitor to reduce a change in print quality caused by the exchange of ink cartridges. When the ink cartridges are exchanged, a control signal is fed from a host computer in the recording apparatus to a printing preparatory signal-generating circuit. The signal-generating circuit changes a charging time of a capacitor and thereby changes the terminal voltage value of the capacitor at the charging time. The drive power supplied to the piezoelectric elements of the ink jet cartridge is then adjusted on the basis of the terminal voltage of the capacitor to limit changes in the print quality due to the exchange of the ink cartridges.
The '803 patent utilizes a capacitor to compensate for different ink cartridges installed in a printer. However, the '803 patent accomplishes this result by adjusting the charging time of the capacitor.